Frances Tiafoe advanced to the U.S. Open semifinals for the second time in three years after his quarterfinal opponent, Grigor Dimitrov, retired due to injury in the fourth set. Tiafoe was leading 6-3, 7-6 (5), 6-3, 4-1 when Dimitrov, who had been struggling with a hamstring issue and received treatment, was unable to continue. Tiafoe will face Taylor Fritz in an all-American semifinal, ensuring a U.S. player in the men’s final.